@davew I think it is not only the problem, to find the podcast on the main directories, but that a lot of podcast are published using services, so that it is sometimes not even possible to simply follow their local sites RSS feed :(
I am currently trying to make Podcasts also a first class citizen of the Fediverse but it is not as easy as I thought. It seems that quite some sites do not even use local podcasting plugins any more, looking at the number of downloads.